CVE-2025-66491CWE-295

CVE-2025-66491

Medium · published December 9, 2025

CVSS v3.1
5.9
EPSS
0%
Percentile
11.9
In the wild
Unconfirmed
What it is

Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.

The record
Technical detail
CVSS v3.1
5.9 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00221 · 11.9th percentile
Weakness
CWE-295 · Improper Certificate Validation
Published
2025-12-09T06:16Z
Affected products (1)
ProductVersionsFixed in
traefik/traefik≥ 3.5.0, < 3.6.33.6.3
References (3)
https://github.com/traefik/traefik/commit/14a1aedf5704673d875d210d7bacf103a43c77e4 · [email protected]https://github.com/traefik/traefik/releases/tag/v3.6.3 · [email protected]https://github.com/traefik/traefik/security/advisories/GHSA-7vww-mvcr-x6vj · [email protected]
EPSS history
Timeline
  • 09 DEC 00:38Z
    Traefik has Inverted TLS Verification Logic in its ingress-nginx Provider
    cvelistv5